Mix the nectarines and blueberries with the lemon juice and the preserving sugar and let stand for about 1 hour. Then stir again and put it on the stove. Bring to the boil, stirring constantly, and simmer for about 15 minutes (stir constantly, otherwise it will burn!)
Now carefully puree (this can also be done before cooking, because of the risk of burns!) And pour into twist-off glasses. Turn the lid and let cool down.